Fuel injection system for an internal combustion engine

ABSTRACT

An electromagnetically actuated valve has a magnetizing winding and has an open state and a closed state and is operative for injecting fuel into an engine cylinder when in said open state. A first current source is operative for establishing a flow of a first current through the magnetizing winding of the valve at a time synchronized with crankshaft rotation and for a time interval varying in dependence upon at least one variable engine operating condition, preferably the rate of air inflow into the engine air-intake passage, to cause the valve to assume one of its two states upon initiation of the flow of such first current and to cause the valve to assume the other of its two states upon termination of the flow of said first current. A second current source is operative during the time of transition of the valve from one to the other of its two states and establishes during such transition the flow of a second current through the magnetizing winding of the valve in the form of a current pulse having a duration equal to a fraction of said time interval, in order to quicken such transition.

United States Patent Lapple et a1.

FUEL INJECTION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE [75] Inventors: Egon L'aipple, Kornwestheim; Peter Schmidt, Schwieberdinger, both of Germany [73] Assignee: Robert Bosch GmbI-I, Stuttgart,

Germany [22] Filed: Aug. 31, 1973 [21] Appl. No.: 393,683

[30] Foreign Application Priority Data Sept. 1, 1972 Germany 2243052 [52] US. Cl. 123/32 EA [51] Int. Cl. F02M 51/00 [58] Field of Search 123/32 EA; 317/123 [56] References Cited UNITED STATES PATENTS 2,077,259 4/1937 Planiol 123/32 EA 2,468,917 5/1949 Booth 123/32 EA 3,565,048 2/1971 Monpetit 123/32 EA 3,739,757 6/1973 Ohtani et al 123/32 EA 3,768,449 10/1973 Lindberg 123/32 EA 3,810,449 5/1974 Chollet et al 123/32 EA Primary ExaminerCharles J. Myhre Assistant E.raminer -Joseph Cangelosi Attorney, Agent, or FirmMichael S. Striker [57] ABSTRACT An electromagnetically actuated valve has a magnetizing winding and has an open state and a closed state and is operative for injecting fuel into an engine cylinder when in said open state. A first current source is operative for establishing a flow of a first current through the magnetizing winding of the valve at a time synchronized with crankshaft rotation and for a time interval varying in dependence upon at least one variable engine operating condition, preferably the rate of air inflow into the engine air-intake passage, to cause the valve to assume one of its two states upon initiation of the flow of such first current and to cause the valve to assume the other of its two states upon termination of the flow of said first current. A second current source is operative during the time of transition of the valve from one to the other of its two states and establishes during such transition the flow of a second current through the magnetizing winding of the valve in the form of a current pulse having a duration equal to a fraction of said time interval, in order to quicken such transition.

U.S. Patent Oct. 21, 1975 Sheet 1 of? 3,913,536

Fig.1

FUEL INJECTION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION ergized a time synchronized with crankshaft rotation and for a time interval varying in dependence upon at least one variable engine operating condition. Most particularly, the invention relates to systems wherein the magnetizing winding is energized for a time interval varying in dependence upon the air inflow rate, with a suitable control circuit being provided to match the quantity of fuel injected into the engine cylinder per combustion cycle to the quantity of air entering such cylinder during the associated piston intake stroke.

In systems of this type, limitations are put upon the precision with which the quantity of fuel injected into an engine cylinder during one combustion cycle can be controlled. The quantity of fuel injected into an engine cylinder during one combustion cycle cannot be very precisely controlled because of the finite length of time the valve requires for undergoing a transition from closed to open state, and because of the finite length of time the fuel-injection valve requires for undergoing a transition from open to closed state. The firstmentioned time results from the fact that the magnetizing current flowing in the magnetizing winding of the fuel-injection valve required a certain amount of time to build up from zero to a value sufficient to open the valve. The second-mentioned time results from the fact that the magnetizing current flowing in the magnetizing winding of the fuel injection valve cannot be brought to zero in zero time and furthermore results from the fact that the magnetizable material of the electromagnetically actuated valve may exhibit some residual magnetization when the magnetizing winding is deenergized. These difficulties are encountered in particular with magnetic valves serving for the direct injection of fuel, especially into the cylinders of diesel engines, because the pressure with which the fuel must be injected must substantially higher than the pressure of compressed air in the engine cylinder, requiring a fuelinjection valve capable of developing relatively high magnetic forces.

SUMMARY OF THE INVENTION It is the general object of the present invention to provide a fuel-injection system of the above described kind wherein the quantity of fuel injected into an engine cylinder per combustion cycle can be more precisely controlled than was the case in the prior art.

It is a more particular object of the present invention to provide a fuel-injection system the electromagnetic fuel-injection valves whereof open more quickly and close more quickly than with known fuel-injection systems of the type in question.

It is a still more specific object to provide a fuelinjection system provided with circuit means for generating valve-opening control pulses operative for opening the valves for a time interval corresponding very closely to the duration of such control pulses, with the duration of such control pulses varying in dependence upon at least one variable engine operating condition, particularly varying in dependence upon the inflow rate of air into the engine air-intake passage. It is in particular desired to provide as part of such system electrical circuitry capable of establishing a closer correspondence between the open time of the fuel-injection valve and the duration of the valve-opening control pulse, by shortening the time required for the valve to close and- /or open.

This object, and others which will become more understandable from the following description of specific embodiments, can be met, according to one advantageous concept of the invention by providing, in the fuel'injection system of an internal combustion engine comprised of at least one engine cylinder, a piston movable in said engine cylinder, and an engine crankshaft coupled to said piston, in combination, electromagnetically actuated valve means comprising a magnetizing winding, said valve means having an open state and a closed state and being operative in said open state for injecting fuel into the engine cylinder. First current source means is operative for establishing a flow of a first current through the magnetizing winding at a time synchronized with crankshaft rotation and for a time interval varying in dependence upon at least one variable engine operating condition, to cause the fuelinjection valve to assume one of its two states upon initiation of the flow of said first current and to cause the fuel-injection valve to assume the other of its two states upon termination of the flow of said first current. Second current source means is operative during the time of transition of said valve means from the open to the closed state and/or during the time of transition of said valve means from the closed to the open state, and establishes during the time of such transition or transitions the flow of a second current through said magnetizing winding in the form of a current pulse having a duration equal to a fraction of said time interval, in order to quicken such transition or transitions.

The novel featureswhich are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 depicts in schematic manner a four-stroke four-cylinder internal combustion engine provided with a fuel-injection system and an electronic control circuit for the fuel-injection valves of the system:

FIG. 2 depicts a circuit operative for energizing the fuel-injection valves of the system;

FIG. 2a depicts in functional block diagram form a circuit for cntrolling the operation of the circuit of FIG.

FIG. 3 depicts in graphical form several aspects of the operationof the circuit of FIGS. 2 and 2a;

FIG. 4 depicts a circuit operative for energizing and de-energizing the fuel-injection valves of the system;

FIG. 4a depicts in functional block diagram form a circuit for controlling the operation of the circuit of FIG. 4; and

FIG. 5 depicts in graphical form several aspects of the operation of the circuit of FIGS. 4 and 4a.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral generally designates an internal-combustion engine provided with four electromagnetically actuatable fuel-injection valves 11, each of which receives fuel from a distributor 12 via a respective one of four fuel conduits 13. An electromotor-driven fuel pump 15 pumps fuel out of a fuel tank, and a pressure regulator 16 maintains the fuel in the fuel conduits at a substantially constant pressure. The fuel-injection system of the engine is comprised of a control circuit, described in more detail below, which is triggered in synchronism with the rotation of the engine crankshaft 17, by means of a triggering stage coupled to the crankshaft l7 and generally designated by numeral 18. The control circuit is triggered once per crankshaft rotation in this embodiment and, when so triggered, generates a valve-opening control pulse 19 which is applied to the magnetizing windings 47 of the fuel-injection valves 11, in a manner described below. The duration of each valve-opening control pulse 19 determines the length of time that the fuel-injection valve 11 remains open, and accordingly the quantity of fuel that will be injected by the valve during such time. There is a close correspondence between the quantity of fuel injected by the valve and the length of time the valve remains open, due to the fact that the fuel in the fuel conduits 13 is maintained at substantially constant pressure.

The valve-opening control pulses 19 are generated by a monostable multivibrator circuit generally designated by numeral 20. The multivibrator 20 is comprised of a normally conductive input transistor 21 and a normally non-conductive output transistor 23. A resistor 22 connects the collector of transistor 21 to the base of transistor 23. Furthermore, the multivibrator 20 includes an energy-storing timing component, here in the form of a transformer having a primary winding 24 and a secondary winding 27. It is emphasized, however, that use could likewise be made of a capacitor as the energystoring timing component, or any combination of capacitors and/or inductive components.

The primary winding 24 of the timing transformer is connected in series with a resistor 25 which in turn has its other terminal connected to the negative voltage supply line 26 of the circuit. The secondary winding 27 of the transformer is inductively coupled to the primary winding 24 thereof by means of a slidable iron core 28. The slidable iron core 28 is connected by a linkage rod with the diaphragm of a pressure-responsive diaphragm arrangement 31. The pressure-responsive diaphragm arrangement 31 communicates with the engine airintake passage 30 at a location downstream of the gaspedal-controlled throttle valve32. Depending upon the air pressure prevailing in that portion of intake passage 30, the pressure-responsive diaphragm in unit 31 will be moved in one or the other direction, to a greater or lesser extent, thereby effecting similar movements of the iron core 28, and thereby effecting variations in the inductive coupling between primary winding 24 and secondary winding 27. If the pressure in intake passage 30 falls, for example when the throttle valve 32 is closed, the iron core 28 will be drawn upwards in the direction of the arrow, causing a reduction in the coupling between windings 24 and 27. Conversely, if the pressure in intake passage 30 rises, for example when the throttle valve 32 is fully opened, the iron core 28 will be lowered, causing an increase in the coupling between windings 24 and 27.

In conventional monostable multivibrator fashion, one terminal of the secondary winding 27 is connected at circuit junction P to the junction between two resistors 33, 34. Resistors 33, 34 act as a voltage divider connected across the positive voltage supply line 35 and the negative voltage supply line 26. The other terminal of secondary winding 27 is connected, via a diode 36, with the base of the input transistor 21, the emitter of which is connected to the positive voltage supply line 35. Both the input transistor 21 and the output transistor 23 are of the pnp conductivity type.

The means 18 for generating triggering pulses for triggering monostable multivibrator 20 is located within the housing of a non-illustrated ignition distributor unit associated with the engine ignition system. The triggering means 18 is comprised of a two-lobed cam 37 coupled to a distributor shaft 38, which is in turn coupled to the engine crankshaft 17. Switch member 39 is biased in the open direction by non-illustrated biasing means, and the two lobes of cam 37 act upon the switch member 39 to press it into electrical engagement with stationary terminal 42. Switch member 39 is connected to the negative voltage supply line 26 by means of a resistor 40. Connected to the junction between resistor 40 and the switch member 39 is a differentiating capacitor 41 and a resistor 44 which connects capacitor 41 to the positive voltage supply line 35. When one of the lobes of cam 37 presses switch member 37 into electrical engagement with terminal 42, it does so for a time interval corresponding to one quarter of a rotation of the distributor shaft 38.

Each time that switch 39, 42 is closed, monostable multivibrator 20 is triggered into its unstable state, the circuit 20 remaining in this unstable state for a time interval ti dependent upon the inductive coupling between the primary winding 24 and secondary winding 27 of the multivibrator timing transformer. In order to trigger the monostable circuit 20, the input transistor 21 must be rendered non-conductive, and this is accomplished by connecting a diode 43 between the junction of components 41, 44 and the base of input transistor 21; As long as the switch 39, 42 remains open, charging current can flow through differentiating capacitor 41, and the voltage across the capacitor 41 will tend to charge up to the full voltage across voltage source 51. When switch 39, 42 is closed, the voltage at the left-hand capacitor terminal will rise to the positive battery voltage, so that the voltage at the right-hand capacitor terminal will assume a value in excess of the voltage at the positive battery terminal. As a result, the voltage applied to the base of transistor 21, via diode 43, will be higher than the emitter voltage of transistor 21, so that transistor 21 becomes non-conductive.

When transistor 21 becomes non-conductive, its collector voltage falls markedly, and this markedly lowvalue. It is to be noted that the potential at the terminal of winding 27 connected to circuit junction P is sub stantially fixed at a value established by the voltage divider 33 34. When the feedback voltage across secondary winding 27 decreases to a predetermined value, the base voltage of transistor 21 becomes sufficiently negative relative to the emitter voltage thereof to render transistor 21 conductive again. When transistor 21 becomes conductive again, it renders non-conductive the output transistor 23, via the coupling resistor 22. The output voltage pulse 19, of duration ti, is taken off the collector of output transistor 23.

The valve-opening control pulse 19, of duration ti, is a gating or enabling pulse, which is applied to the control input of a power amplifier stage 45. When the gating pulse 19 is applied to the control input of stage 45, stage 45 permits the flow of energizing current from the positive voltage supply line 35, through the diode 49 and resistor 48, through the magnetizing windings 47 of the four fuel-injection valves 11, through a current path internal to the power amplifier stage 45, to the negative voltage supply line 26.

FIG. 2 depicts circuit details of one embodiment of the power amplifier stage 45. The stage 45 is comprised of a power amplifier transistor 46 whose collector is connected to one terminal of the magnetizing winding 47 of one of the fuel-injection valves 11. In FIG. 2, only a single one of the magnetizing windings 47 is depicted. The other terminal of the illustrated winding 47, and the corresponding terminals of the other magnetizing windings 47, are connected to the positive voltage supply line 35 by way of a shared circuit branch comprised of diode 49 and resistor 48.

When the monostable multivibrator generates the valve-opening control pulse 19, this pulse is applied to the base of transistor 46, rendering that transistor conductive. Accordingly, energizing current flows from the positive line 35, through the magnetizing winding 47, through the collector-emitter path of transistor 46, to ground, for the duration ti of the valve-opening control pulse 19. While the magnetizing winding 47 is thusly energized, the respective fuel-injection valve 11 is maintained open. Upon termination of the valveopening c'ontrol pulse 19, the forward-bias of transistor 46 is terminated, and transistor 46 becomes nonconductive. However, the magnetizable material of the valve 11 may exhibit some residual magnetism, thereby slowing the transition of the valve 11 from its open state to its closed state. The other circuit components shown in FIG. 2 are provided to quicken the closing of the valve 11." This is accomplished in FIG. 2 by establishing, upon termination of the flow of the magnetizing or first current, the flow of a second demagnetizing current flowing fora very short time through the magnetizing winding in the opposite direction.

The manner in which this short-lasting second or demagnetizing currenti s made to flow will become clear from a description of the other circuit components in FIG. 2.

The circuit of FIG. 2 is comprised of a highinductance inductor coil 54 provided with an iron core 53. The coil 54 has a first terminal connected to the positive voltage supply line 35, and has a second terminal connected to the collector of a transistor 55, transistor 55 constituting a first electronic switch. When transistor 55 is rendered conductive, current will flow from positive line 35 through coil 54, through the collector-emitterpath of transistor 55 to ground. If transistor 55 is subsequently rendered non-conductive, there will be an abrupt termination of the flow of current in coil 54, inducing thereacross a very sizable voltage surge.

An energy-storing capacitor 60 is provided to store the energy which accumulates in inductor 53, 54 before the interruption of current flow just mentioned. One terminal of capacitor 60 is connected directly to one terminal of inductor coil 54. The other terminal of coil 54 is connected to the other terminal of capacitor 60 via a charging diode 57, which permits charging current to flow into capacitor 60 from coil 54, but prevents discharging of capacitor 60 through coil 54. When the current flow in coil 54 is interrupted, in the manner just mentioned, the voltage pulse induced across coil 54 will be applied across capacitor 60 and will quickly effect charging of the latter, the energy which was stored in coil 54 now being transferred to the capacitor 60.

After capacitor 60 has been charged in this manner, it cannot discharge, except through a second electronic switch, here in the form of a thyristor 58. When power transistor 46 becomes non'conductive, at the end of the valve-opening control pulse 19, the current flowing through the valve magnetizing winding 47 is interrupted. At this moment, thyristor 58 is rendered conductive. As a result, capacitor 60 will discharge, the capacitor discharge current Ie flowing through the thyristor 58, through the magnetizing winding in upwards direction (as viewed in FIG. 2), through a discharge diode 56, and thence to ground through the collectoremitter path of transistor 55. It is to be noted that transistor 55 will be conductive at this time, in order to effect a build-up of current flow in the inductor coil 54, in anticipation of the next charging of capacitor 60. Specifically, transistor 55 is rendered conductive at the end of the valve-opening control pulse 19, simultaneously with the rendering non-conductive of transistor 46, and simultaneously with the rendering conductive of thyristor 58. Transistor 55 is maintained conductive for a time period ta, and is then rendered nonconductive, so as to again interrupt the current flow in coil54, to thereby again induce across the latter a charging voltage which will charge the capacitor 60.

This sequence of events is clear from the four graphs depicted in FIG. 3. The train of pulses designated 19 indicates the valve-opening control pulses 19 described before. The train of pulses designated 61, each pulse being of duration ta, indicates the times during which the first electronic switch 55 and the second electronic switch 58 are maintained conductive. The train of pulses designated Ie indicates the flow of capacitor discharge current Ie through the magnetizing winding 47, through diode 56, and through the collector-emitter path of transistor 55, to ground. It will be seen that the demagnetizing current pulses le are of very short duration, being needed only during the short time of the transistor of the valve 11 from its open state to its closed state. It will be noted that the leading edges of the pulses 61 and le coincide with the trailing edge of the pulses 19. 1

FIG. 2a indicates, in schematic block diagram form, a circuit for rendering first, second and third electronic switches 55, 58, 46 conductive and non-conductive in the proper sequence, as depicted in the graph of FIG. 3

In FIG. 2a, the valve-opening control pulse 19 of duration ti is applied to a differentiator 100 which produces at its output a positive-going voltage spike and a negative-going voltage spike, corresponding respectively to the leading and trailing edges of pulse 19. These two voltage spikes are applied to the input of a half-wave rectifier 101 which passes only the positivegoing spike and applies the same to a monostable multivibrator 102 having an unstable state of duration ta. The output pulse of duration ta is applied to the gate 59 of thyristor 58 and also to the base of transistor 55, in FIG. 2. The base of transistor 46 in FIG. 2 may be connected directly to the collector of transistor 23 in FIG. 1.

FIG. 4 depicts another embodiment of the power amplifying stage 45 of FIG. 1. In the embodiment of FIG. 4 means are provided not only for quickening the transition of the valve 1 1 from open to closed state, but also for quickening the transition from the closed to the open state.

Those components in FIG. 4 which correspond exactly to the components of FIG. 2 are identified by the same reference numerals, for the sake of simplicity.

FIG. 4 differs from FIG. 2 in the provision of an additional capacitor 65 having a first terminal connected to the positive voltage supply line 35, and having a second terminal connected to the upper terminal (as viewed in FIG. 4) of magnetizing winding 47. A charging diode 67 is connected between the lower terminal of coil 54 and the lower terminal of additional capacitor 65. When the current flow in coil 54 is interrupted, in the manner described with respect to FIG. 2, not only capacitor 60, but also additional capacitor 65, will become charged, via respective charging diodes 57 and 67. However, the times of discharge of the two capacitors 65 and 60 in FIG. 4 are not the same. Capacitor 65 will become discharged when the valve-opening control pulse 19 is applied to the base of transistor 46, thereby providing a path for the flow of magnetizing current from the positive line 35, through diode 49 and resistor 48, through the magnetizing winding 47 itself, and through the collector-emitter path of transistor 46, to ground. However, superimposed upon this first current flow will be a second current flow, namely the very short-lasting surge of discharge current flowing out of capacitor 65 through magnetizing winding 47, through the collector-emitter path of transistor 46, to ground. This very short-lasting surge of discharge current from capacitor 65 will effect a considerable increase in the magnitude of the magnetizing current passing through magnetizing winding 47 during the transition of the associated valve 1 1 from the closed to the open state, and will thereby quicken this transition.

It should be understood that while transistor 46 is conductive, i.e., for the duration of valve-opening pulse 19, transistor 66 and thyristor 58 will both be nonconductive. However, transistor 55 will be conductive,

i being in fact rendered conductive at the same time as transistor 46, in order to effect a build-up of current through inductor '54, in anticipation of the 7 nextfollowing capacitor-charging operation. i

At the end of valve-opening pulse 19, transistor 46 becomes non-conductive, and energizing current can no longer flow through magnetizing winding 47 in direction from the upper to the lower terminal thereof. However, the magnetizable material of the fuelinjection valve may exhibit some residual magnetism, causing a relatively slow closing of the valve. The closing of the valve is quickened, as in FIG. 2, by establishing a brief flow of demagnetizing current flowing through magnetizing winding in the opposite direction, i.e., in direction from the lower. to the upper terminal thereof. This is accomplished by simultaneously rendering conductive the thyristor 58 and the discharge transistor 66. As a result, charged capacitor 60 discharges, the capacitor discharge current of capacitor 60 flowing through thyristor 58, then through the magnetizing winding 47, then through the collector-emitter path of transistor 66, to ground. This discharge current has the form of a very short-lasting current surge, lasting just long enough to quicken the transition of the electromagnetic valve from its open to its closed state.

Next, first electronic switch 55, second electronic switch 58 and fourth electronic switch 66 are simultaneously rendered non-conductive. The rendering nonconductive of switch 55 effects charging of capacitors 60 and 65, in the manner described. The rendering non-conductive of switches 58 and 66 at this time prevents the diverting of current away from capacitors 60 and 65 and prevents the discharging of capacitors 60 and 65.

The components shown in FIG. 4 in broken lines represent the othersof the four electromagnetic valves 11 and respective discharge thyristors therefor.

FIG. 5 depicts in graphical form the timing sequence of the various electronic switches just described. The pulse train comprised of pulses 19 represents the valveopening control pulses 19. For the duration of each of these pulses, the transistor 46 in FIG. 4 is conductive.

The pulse train designated 68 indicates the times during which transistor 66 and thyristor 58 are conductive.

It will be seen that transistor 66 and thyristor 58 are rendered conductive at the end of the valve-opening pulse 19. The pulse train comprised of pulses of duration tb indicates the times during which transistor 55 is conductive. It will be noted that transistor 55 is rendered conductive at the same time that transistor 46 is rendered conductive, at the time of the leading edge of valve-opening control pulse 19. However, transistor 55 remains open for a time interval tb. It will also be noted that transistor 66 and thyristor 58 (pulse train 68) are rendered non-conductive at the same time that transistor 55 is rendered non-conductive.

FIG. 4a shows in. schematic block diagram form a merely exemplary circuit for the rendering conductive and non-conductive of the electronic switches 55, 58, 46 and 66 of FIG. 4, in the sequence just described.

The base of transistor 46 in FIG. 4 can be connected directly to the collector of transistor 23 in FIG. 1, so as to render transistor 46 conductive during the valveopening pulses 19. Each valve-opening pulse is furthermore appliedto a differentiator 103, which generates a positive-going voltage spike and a negative-going voltage spike, in correspondence to the leading and trailing edges of pulse 19. A half-wave rectifier 104 passes only the positive pulse and triggers flip-flop FFl to that one of its two states in which it applies a forward-biasing voltage to the base of transistor 66 in FIG. 4. The first output of flip-flop FFl is also connected to the gate of thyristor 58 to render the same conductive at the same time as transistor 66. It will be evident that transistor 66 and thyristor 58 become conductive at the time of the trailing edge of pulse 19.

As just mentioned, the differentiator 103 generates positive-going and negative-going voltage spikes in correspondence to the leading and trailing ends of pulse 19. These voltage spikes are applied to a half-wave rectifier 105 which passes only the positive-going voltage spike to the trigger input of a monostable multivibrator 106 having an unstable state of duration tb. As soon as multivibrator 106 is triggered, its output pulse is applied to the base of transistor 55, to render the same conductive at the time of the leading edge of pulse 19, and to maintain transistor 55 conductive for a time interval tb. The output pulse of multivibrator 106 is also applied to a differentiator 107 which generates a positive-going and a negative-going voltage spike in correspondence to the leading and trailing ends of the output pulse of multivibrator 106. These voltage spikes are applied to half-wave rectifier 108 which passes only the negative-going voltage spike and applies it to the second input of flip-flop FFl, thereby rendering transistor 66 and thyristor 58 non-conductive.

A fuel-injection system such as shown in FIG. 1 was provided with an experimental circuit such as that shown in H6. 4. The time required for the fuelinjection valves to undergo a transition from closed to open state was reduced from 2.5 milliseconds to 0.5 milliseconds. The time required for the valves to undergo a transition from open to closed state was reduced from 5 milliseconds to l millisecond.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of circuits and constructions differing from the types described above.

While the invention has been illustrated and described as embodied in the fuel-injection system of an internal combustion engine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended:

1. In the fuel-injection system of an internal combustion engine comprised of at least one engine cylinder, a piston movable in said cylinder, and an engine crankshaft coupled to said piston, in combination, electromagnetically actuated valve means comprising a magnetizing winding, said valve means having an open state and a closed state and being operative in said open state for injecting fuel into said engine cylinder; first current source means operative for establishing a flow of a first current through said magnetizing winding at a time synchronized with crankshaft rotation and for a time interval varying in dependence upon at least one variable engine operating condition, to cause said valve means to assume one of said states upon initiation of the flow of said first current and to cause said valve means to assume the other of said states upon termination of the flow of said first current; and second current source means operative during the time of transition of said valve means from one of said states to the other of said states for establishing during such transition the flow of a second current through said magnetizing winding in the form of a current pulse, in order to quicken such transition, wherein said first current source means comprises means for establishing said flow of said first current through said magnetizing winding in a first direction, and wherein said second current source means comprises energy-storing inductor means, first energy-storing capacitor means, second energy-storing capacitor means, means for periodically establishing a flow of current through said inductor means, means for periodically interrupting the flow of current through said inductor means to induce thereacross a voltage surge, means connecting said inductor means to said first and second capacitor means for charging said first and second capacitor means, means connecting said first capacitor means to said magnetizing winding and operative for establishing said flow of said second current through said magnetizing winding in said first direction during the transition of said valve means associated with commencement of flow of said first current by discharging said first capacitor means through said magnetizing winding in said first direction, and means connecting said second capacitor means to said magnetizing winding and operative for establishing said flow of said second current through said magnetizing winding in opposite second direction during the transition of said valve means associated with termination of flow of said first current by discharging said second capacitor means through said magnetizing winding in said second direction.

2. In the fuel'injection system of an internal combustion engine comprised of at least one engine cylinder, a piston movable in said cylinder, and an engine crankshaft coupled to said piston, in combination, electromagnetically actuated valve means comprising a magnetizing winding, said valve means having an open state and a closed state and being operative in said open state for injecting fuel into said engine cylinder; first current source means operative for establishing a flow of a first current through said magnetizing winding at a time synchronized with crankshaft rotation and for a time interval varying in dependence upon at least one variable engine operating condition, to cause said valve means to assume one of said states upon initiation of the flow of said first current and to cause said valve means to assume the other of said states upon termination of the flow of said first current; and second current source means operative during the time of transition of said valve means from one of said states to the other of said states for establishing during such transition the flow of a second current through said magnetizing winding in the form of a current pulse, in order to quicken such transition, wherein said first apd econd current source means together comprise a voltage source having a positive terminal and a negative terminal and first and second voltage supply lines of which one is connected to said positive terminal and the other is connected to said negative terminal, an inductor having a first terminal connected to said first voltage supply line, first electronic switch means connecting the second terminal of said indcutor to said second voltage supply line and operative when conductive for permitting a build-up of current flow in said inductor and op erative when rendered non-conductive for interrupting the flow of current in said inductor and thereby inducing thereacross a voltage surge, an energy-storing capacitor having a first terminal connected to said first terminal of said inductor, a charging diode connecting the second terminal of said capacitor to said second terminal of said inductor and having such a polarity as to carry charging current into said capacitor from said inductor when the current flow in said inductor is interrupted, said magnetizing winding having a first terminal connected to said first voltage supply line and having a second terminal, discharge means connected to said first terminal of said magnetizing winding and connected to said second voltage supply line and operative for providing a path for the flow of current from said first terminal of said magnetizing winding to said second voltage supply line, second electronic switch means connecting said second terminal of said magnetizing winding to said second terminal of said capacitor and operative when conductive for carrying capacitor discharge current from said second terminal of said capacitor to said second terminal of said magnetizing winding so that said discharge current can flow to said second voltage supply line through said discharge means, and third electronic switches means connected between said second terminal of said magnetizing winding and said second voltage supply line and operative when conductive for permitting the flow of current through said magnetizing winding from the first to the second terminal of said magnetizing winding and thence to said second voltage supply line, crankshaftsynchronized means operative for establishing said flow of said first current through said magnetizing winding by rendering said third electronic switch means conductive at a time synchronized with crankshaft rotation and for a time interval varying in dependence upon at least one variable engine operating condition, means operative when said third switch means becomes nonconductive at the end of said time interval for causing said second electronic switch means to become conductive to discharge said capacitor through said magnetizing winding in direction from the second terminal of said magnetizing winding to said first terminal thereof, means for periodically rendering said first electronic switch means conductive to effect a build-up of current flow therein, and means for periodically rendering said first switch means non-conductive to effect charging of said capacitor.

3. The system defined in claim 1, wherein said first current source means comprises means for establishing said flow of said first current through said magnetizing winding in a firstdirection, and wherein said second current source means comprises means operative for establishing said flow of said second current through said magnetizing winding in opposite second direction during the transition of said valve means associated with terminationof the flow of said first current, in order to quicken such transition.

4. The system defined in claim 1, wherein said first current source means comprises means for establishing said flow of said first current through said magnetizing winding in a first direction, and wherein said second current source means comprises means operative for establishing said flow of said second current in said first direction during the transition of said valve means associated with initiation of the flow of said first current, in order to quicken such transition.

5. The system defined in claim 1, wherein said first current source means comprises means for establishing said flow of said first current through said magnetizing winding in a first direction, and wherein said second current source means comprises means operative for establishing said flow of said second current in said first direction during the transition of said valve means associated with initiation of the flow of said first current and means operative for establishing said flow of said second current in opposite second direction during the transition of said valve means associated with termination of the flow of said first current, in order to quicken such transitions.

6. The system defined in claim 1, wherein said second current source means comprises energy-storing means, means for periodically storing energy in said energystoring means, and means connecting said energystoring means to said magnetizing winding and operative for transferring the energy stored in said energystoring means to said magnetizing winding during the time of transition of said valve means from one of said states to the other of said states by establishing said flow of said second current during the time of such transition.

7. The system defined in claim 1, wherein said second current source means comprises energy-storing inductor means and energy-storing capacitor means, means for periodically establishing a flow of current through said inductor means, means for periodically interrupting the flow of current through said inductor means to induce thereacross a voltage surge, means connecting said inductor means to said capacitor means and operative for applying said voltage surge across said capacitor means to effect charging of the latter, and means connecting said capacitor means to said magnetizing winding and operative for establishing said flow of said second current during the time of said transition by discharging said capacitor means through said magnetizing winding.

8. The system defined in claim 2, wherein said first and second current source means together comprise a diode connecting said first terminal of said magnetizing winding to said first voltage supply line.

9. The system defined in claim 8, wherein said discharge means comprises a diode connected between said first terminal of said magnetizing winding and said second terminal of said inductor.

10. The system defined in claim 9, wherein said secondelectronic switch means comprises a thyristor.

11. The system defined in claim 2, wherein said dis charge means comprises fourth electronic switch means connected between said first terminal of said magnetizing winding and said second voltage supply line, and wherein said first and'second current source means together include means for rendering said fourth electronic switch means conductive when said second electronic switch means is conductive, to provide for said capacitor a complete discharge current which includes said magnetizing winding.

12. The system defined in claim 2, wherein said means for periodically rendering said first switch means conductive comprises means for periodically rendering said first switch conductive for conduction time intervals of about one millisecond.

13. The system defined in claim 2, wherein said first terminal of said magnetizing winding is connected to said first voltage supply line via a circuit branch composed of the series connection of a diode and a resistor.

14. The system defined in claim 2, wherein said second current source means comprises an additional capacitor having a first terminal connected to said first switch means. 

1. In the fuel-injection system of an internal combustion engine comprised of at least one engine cylinder, a piston movable in said cylinder, and an engine crankshaft coupled to said piston, in combination, electromagnetically actuated valve means comprising a magnetizing winding, said valve means having an open state and a closed state and being operative in said open state for injecting fuel into said engine cylinder; first current source means operative for establishing a flow of a first current through said magnetizing winding at a time synchronized with crankshaft rotation and for a time interval varying in dependence upon at least one variable engine operating condition, to cause said valve means to assume one of said states upon initiation of the flow of said first current and to cause said valve means to assume the other of said states upon termination of the flow of said first current; and second current source means operative during the time of transition of said valve means from one of said states to the other of said states for establishing during such transition the flow of a second current through said magnetizing winding in the form of a current pulse, in order to quicken such transition, wherein said first current source means comprises means for establishing said flow of said first current through said magnetizing winding in a first direction, and wherein said second current source means comprises energy-storing inductor means, first energy-storing capacitor means, second energy-storing capacitor means, means for periodically establishing a flow of current through said inductor means, means for periodically interrupting the flow of current through said inductor means to induce thereacross a voltage surge, means connecting said inductor means to said first and second capacitor means for charging said first and second capacitor means, means connecting said first capacitor means to said magnetizing winding and operative for establishing said flow of said second current through said magnetizing winding in said first direction during the transition of said valve means associated with commencement of flow of said first current by discharging said first capacitor means through said magnetizing winding in said first direction, and means connecting said second capacitor means to said magnetizing winding and operative for establishing said flow of said second current through said magnetizing winding in opposite second direction during the transition of said valve means associated with termination of flow of said first current by discharging said second capacitor means through said magnetizing winding in said second direction.
 2. In the fuel-injection system of an internal combustion engine comprised of at least one engine cylinder, a piston movable in said cylinder, and an engine crankshaft coupled to said piston, in combination, electromagnetically actuated valve means comprising a magnetizing winding, said valve means having an open state and a closed state and being operative in said open state for injecting fuel into said engine cylinder; first current source means operative for establishing a flow of a first current through said magnetizing winding at a time synchronized with crankshaft rotAtion and for a time interval varying in dependence upon at least one variable engine operating condition, to cause said valve means to assume one of said states upon initiation of the flow of said first curret and to cause said valve means to assume the other of said states upon termination of the flow of said first current; and second current source means operative during the time of transition of said valve means from one of said states to the other of said states for establishing during such transition the flow of a second current through said magnetizing winding in the form of a current pulse, in order to quicken such transition, wherein said first and second current source means together comprise a voltage source having a positive terminal and a negative terminal and first and second voltage supply lines of which one is connected to said positive terminal and the other is connected to said negative terminal, an inductor having a first terminal connected to said first voltage supply line, first electronic switch means connecting the second terminal of said indcutor to said second voltage supply line and operative when conductive for permitting a build-up of current flow in said inductor and operative when rendered non-conductive for interrupting the flow of current in said inductor and thereby inducing thereacross a voltage surge, an energy-storing capacitor having a first terminal connected to said first terminal of said inductor, a charging diode connecting the second terminal of said capacitor to said second terminal of said inductor and having such a polarity as to carry charging current into said capacitor from said inductor when the current flow in said inductor is interrupted, said magnetizing winding having a first terminal connected to said first voltage supply line and having a second terminal, discharge means connected to said first terminal of said magnetizing winding and connected to said second voltage supply line and operative for providing a path for the flow of current from said first terminal of said magnetizing winding to said second voltage supply line, second electronic switch means connecting said second terminal of said magnetizing winding to said second terminal of said capacitor and operative when conductive for carrying capacitor discharge current from said second terminal of said capacitor to said second terminal of said magnetizing winding so that said discharge current can flow to said second voltage supply line through said discharge means, and third electronic switches means connected between said second terminal of said magnetizing winding and said second voltage supply line and operative when conductive for permitting the flow of current through said magnetizing winding from the first to the second terminal of said magnetizing winding and thence to said second voltage supply line, crankshaft-synchronized means operative for establishing said flow of said first current through said magnetizing winding by rendering said third electronic switch means conductive at a time synchronized with crankshaft rotation and for a time interval varying in dependence upon at least one variable engine operating condition, means operative when said third switch means becomes non-conductive at the end of said time interval for causing said second electronic switch means to become conductive to discharge said capacitor through said magnetizing winding in direction from the second terminal of said magnetizing winding to said first terminal thereof, means for periodically rendering said first electronic switch means conductive to effect a build-up of current flow therein, and means for periodically rendering said first switch means non-conductive to effect charging of said capacitor.
 3. The system defined in claim 1, wherein said first current source means comprises means for establishing said flow of said first current through said magnetizing winding in a first direction, and wherein said second current source means comprises means operative for establishIng said flow of said second current through said magnetizing winding in opposite second direction during the transition of said valve means associated with termination of the flow of said first current, in order to quicken such transition.
 4. The system defined in claim 1, wherein said first current source means comprises means for establishing said flow of said first current through said magnetizing winding in a first direction, and wherein said second current source means comprises means operative for establishing said flow of said second current in said first direction during the transition of said valve means associated with initiation of the flow of said first current, in order to quicken such transition.
 5. The system defined in claim 1, wherein said first current source means comprises means for establishing said flow of said first current through said magnetizing winding in a first direction, and wherein said second current source means comprises means operative for establishing said flow of said second current in said first direction during the transition of said valve means associated with initiation of the flow of said first current and means operative for establishing said flow of said second current in opposite second direction during the transition of said valve means associated with termination of the flow of said first current, in order to quicken such transitions.
 6. The system defined in claim 1, wherein said second current source means comprises energy-storing means, means for periodically storing energy in said energy-storing means, and means connecting said energy-storing means to said magnetizing winding and operative for transferring the energy stored in said energy-storing means to said magnetizing winding during the time of transition of said valve means from one of said states to the other of said states by establishing said flow of said second current during the time of such transition.
 7. The system defined in claim 1, wherein said second current source means comprises energy-storing inductor means and energy-storing capacitor means, means for periodically establishing a flow of current through said inductor means, means for periodically interrupting the flow of current through said inductor means to induce thereacross a voltage surge, means connecting said inductor means to said capacitor means and operative for applying said voltage surge across said capacitor means to effect charging of the latter, and means connecting said capacitor means to said magnetizing winding and operative for establishing said flow of said second current during the time of said transition by discharging said capacitor means through said magnetizing winding.
 8. The system defined in claim 2, wherein said first and second current source means together comprise a diode connecting said first terminal of said magnetizing winding to said first voltage supply line.
 9. The system defined in claim 8, wherein said discharge means comprises a diode connected between said first terminal of said magnetizing winding and said second terminal of said inductor.
 10. The system defined in claim 9, wherein said second electronic switch means comprises a thyristor.
 11. The system defined in claim 2, wherein said discharge means comprises fourth electronic switch means connected between said first terminal of said magnetizing winding and said second voltage supply line, and wherein said first and second current source means together include means for rendering said fourth electronic switch means conductive when said second electronic switch means is conductive, to provide for said capacitor a complete discharge current which includes said magnetizing winding.
 12. The system defined in claim 2, wherein said means for periodically rendering said first switch means conductive comprises means for periodically rendering said first switch conductive for conduction time intervals of about one millisecond.
 13. The system defined in claim 2, wherein said first terminal of said magnetizing winding is connected to said first voltage supply line via a circuit branch composed of the series connection of a diode and a resistor.
 14. The system defined in claim 2, wherein said second current source means comprises an additional capacitor having a first terminal connected to said first voltage supply line and a second terminal, a diode connecting said second terminal of said additional capacitor to said second terminal of said inductor with such a polarity as to effect charging of said additional capacitor when said voltage surge is induced across said inductor, said second terminal of said additional capacitor being connected to said first terminal of said magnetizing winding, so that when said third switch means is rendered conductive said additional capacitor will charge through said magnetizing winding and said third switch means. 